Fuel injection pump



March 3l, 1942.

A. LICHTE ETAL FUEL INJECTION PUMP Filed Aug. 6, i940 2 SheetshSheet l Fig.2

Fig 1 March 3i, 1942. A. LlcHTE ET AL 2,278,395

FUEL INJECTION PUMP Filed Aug. 6, 1940 2 sheets-sheet 2 /n venters /G'FOHNES/e Patented Mar. 31, 1942 UNITED STATE s PATENT OFFICE .l

FUEL INJECTION PUMP lAugust Lichte, Dessau-Alten, and Ernst Kolbe,

Dessau, Germany, assis-nots to Junkers Flugzeug-und-Motorenwerke, A. G., Dessau, Germany, a corporation of Germany Application August s, In Germany 1940, Serial No. 351,600 June 30, 1939 s claims. (c1. a-41) This` invention is directed fuel injection pumps for internal combustion engines, and is particularly directed to the lubrication of such pumps.

Fuel injection pumps of the type under consideration, consist of a pumping piston closely fitting within a. cylinder. Fuel is supplied to the pumping chamber of the cylinder and is forced outwardly therefrom to the engine. Lubricating' than the oil feed pressureiso that lubrication of the piston ceases.

An attempt to overcome this'imeulty has been made by connecting the second groove with the u fuel inlet line to the pump' by means of a bore. By so doing, the oil and fuel pressure in the second annular groove is never higher than the intake pressure to the fuel pump which, of course,

properties, will not dilute or replace the oil lm between the piston and the cylinder walls. Too great an oil supply pressure would mean that an excessive quantity of oil, that is more oil than is needed to lubricate theV piston, would flow past ,the 'piston into the pumping chamber, and there` would be mixed with the fuel and wasted. The difficulty of ascertaining a correct oil feed pressure is complicated because of the increase in fuel pressure in the pumpingchamber during the piston pumping stroke; this increase in 4fuel is less than the oil feed pressure to the pump. Difficulties, however, have been experienced with this construction because the bore, which is obliquely disposed in the pump, creates a compli' cated and expensive piece of construction. Particularly this construction has been unsuccessful 'in the manufacturing of the cylinder blocks inas-l much as during the hardening of the blocks, the

oblique bore very often cracks open at its angular top. and the number of spoiled-and rejected cylinder blocks has been extraordinarily high.

It is an object of the instant invention to produce a fuel pump in which, by means of a very simple construction entirely within the cylinder, a substantially constant pressure differential is maintained between the oil feed pressure and the oil seal pressure.

Another object of theinvention is to construct an oil injection pump, the cylinder block of which pressure being greater than the oil supply pressure so that lfuel is forced between the' cylinder and piston walls, with the result that the lubricantl is diluted or displaced.

In the prior art attempts have been made to achieve the proper lubrication of the pump and a substantially constant oil supply pressure with slow seepage of oil past the piston by providing an annular oil supply groove Yfor the piston, and

an annular oil collection and sealing groove be- A tween the oilsu'pply groove and the pumping chamber, this second groove being so-far removed from the pumping chamber that it remains' constantly covered and sealed regardless of the position of the `piston in the cylinder. This arrangement has not been entirely successful inasmuchvas the reciprocation of the piston builds'up pressure in the second groove, which pressure in time increases to such a degree as to interfere with the proper operation' of the pump. ThisV pressure is created by thesecon'd groove becoming lled with fuel forced down between the piston and cylinder wall during the pumping stroke of the piston, that is during the can be readily machined .and heat treated without cracking, While at the same time an adequate lubricating system for the pump is obtained.

Another object of the invention is to construct a fuel injection pump having a novel oil sealing means by reason ofwhich a mixture of oil and fuel is kept at a minimum, while excess pressures which would interfere with the operation of the pump are avoided.

Another object of the invention is to constructy a fuel injection pump in which the oil pressure in the oil sealing groove is kept appreciably below lthe Voil inlet pressure -during, the entire `working i range of the pump;

Generally these objects are accomplished by' providing the cylinder -or the'l piston with two Y annular grooves', one 'of which is spaced from period when the highest pressure prevails in the f' tively the pumping chamber and constitutes the oil supply, while the other groove is located so that 'communication is established between it and the pumping chamber for a. short time during Va portion of the pistonstroke. This communication may be established by forming the oil seal groove in the cylinder wall and having it communicate with the pumping chamber of u the cylinder through a recess in the piston when the piston is adjacent its outer dead center position, or by leaving at the piston outer dead center position such a small sealing surface between the piston and cylinder walls thatv communication is effecif indirectly, 'established between the groo e and the pumping chamber. In a multicylinder pump, further releasev of pressure from the oil seal grooves can be accomplished by interconnecting the oil seal grooves ofthe various cylinders with each other so that when the pressure is produced in the groove during the pumping stroke in one cylinder, it is released by the suction stroke taking place in a second cylinder. vIf desired the grooves can be formed in the piston instead of in the cylinder wall.

The means by which these objects may be accomplished are shown more clearly in the accompanying drawings in which:

Fig. 1 is a cross sectional view of a portion of a fuel injection pump showing the lubricating construction of this invention, Iwith tlie piston positioned at its outer dead center position in the cylinder.

Fig. 2 is a similar view, but showingthe piston shortly after starting its pumping stroke, and at the instant the oil seal groove is covered by the piston.

Fig. 3 is a similar view, but showing the piston at the position where the fuel inlet port is closed.

Fig. 4 is another similar view, showing the piston at its inner dead center position.

Fig. 5 is a cross sectional view on the line 5-5 of Fi'g. l. I

Fig. 6 is a view similar to Fig. 1, but showin a modified form of the invention in which the oil seal groove is not uncovered when the piston is at its outer dead center position.

Fig. '7 is a view similar to Fig. 1, but showing a modified form ofthe invention as applied to a multi-cylinder pump, and

Fig. 8 is a cross sectional view on the line 8-8 of Fig. 7. Y

In Fig. l the cylinder block 2 is `fitted with a cylinder lining 4 Within which a piston 8 reciprocates. Fuel passes through the fuel inlet 8, through a port Il) in cylinder lining 4, into the pumping chamber I2 of the pump. This construction is typical of fuel injection pumps, the pumped fuel passing from chamber I2 through a check valve, -not shown, to the combustion chamber of the engine.

vTo lubricate piston 6,f-oil is supplied through bore I4 in block 2, through port I6 in cylinder lining 4, to an annular groove I8 formed in the inner surface of cylinder lining 4. It is obvious that oil supplied through bore I4 will lubricate the surfaces of the piston and cylinder lining.-

extending from its-upper surface to aso-called unloading channel 24. Groove 20 is so positioned with respect to unloading channel 24 that when the piston is at its outer dead center position as shown in Fig. 1, groove 20 is uncovered to establish communication from groove 20 through channel 24 and recess 22, into pumping chamber I2, As the piston starts on its pumping stroke, Fig. 2, this communication is out ofi? justv before the top'surface of the piston closes off fuel port Il).l When the fuel inlet port Ill is closed, groove 2l)r is cut off as shown in Fig. 3 by the piston length between the groove and the edge of channel 24., lwhile when the piston 'has reached its Ainner dead center position at the completion of this pumping stroke as shown in Fig. 4, a substantial sealing surface exists between the channel 24 and groove 20.

At the beginning of the pumping stroke of the piston, that is'when the piston is atits outer dead center position, the oil supplied through bore' I4 has a greater pressure than the fuel supplied through bore III into pumping chamber I2, and therefore oil will tend to seepv along the surface of Vthe piston from groove I8 toward groove 20 to lubricate the piston. As the pumping stroke takes place, oil is carried by the piston wall toward groove 20, while at the same time the pressure increase on ther fuel in pumping chamber I2 will tend to force fuel toward groove 28. However, as the pumping stroke increases, the distance from channel 24 to groove 20 also increases, and consequently the oil seal tends to prevent the fuel from reaching groove 20. Hence there is substantially no increase in pressure in the groove 20 due .to the increase pressure in pressure chamber I2 so'that. oil will ow to groove 20. On the return stroke of the piston.

when the outer dead center position is reached,l

communication is established between groove 20 and the pumping chamber so that any excess pressure built up in groove 20 is immediately released. A buiding up of pressure in groove 20 by successive reciprocations of the piston is prevented. Consequently the average pressure in groove 20 at any time, lies' appreciably below the oil feed pressure. and no excess pressures are built up in groove 20 which would interfere with the proper working of the pump. At the same time, oil in groove 20 serves to entire surfacel of the piston.

In Figs. 1 to 5, a direct communication between the groove 20 andpumping chamber I2 is ob-l tained. The piston can be constructed so that, as shown in Fig. 6, an indirect communication is maintained between the groove and the chamber. For example, theunloading channel 24a in piston 6a is so constructed that the surface of the piston always covers groove 20a, but a very little distancel is left between groove 20a and channel 24a. Consequently the fuel vunder excess pressure in groove 20a can escape between the cylinder wall and the piston into channel 24a when the piston is at its outer dead center position. v

The invention can also be used with particular advantage in a multi-piston pump as shown in Figs. '7 and 8. In this pump the cylinder block 30 is provided with a-plurality of cylinders in line, with pistons 32 to 31, respectively, therein.

Each piston is constructed as the piston shown in' Figs. 1 to 5, inclusive, and each cylinder has a pumping chamber 44 from which fuel is passed through check valve 46 to the combustion chamber of'an engine. Fuel is supplied to the pump through a bore 48 common to all the cylinders, each of which is connected to bore 48 by its individual port. Oil is supplied to the pistons and cylinders through a bore 50 common to all the cylinders, through ports for each of the cylinders, respectively, to annular groove 52 in each cylinder wall around each piston. An oil seal groove 54- is formed in each cylinder wall and associated with a so-called unloading channel 56 -which communicates through a recess 58 in the piston head for establishing communication between groove 54 and pumping chamber 44 when the piston is at its outer dead center position. In thismulti-cylinder pump, all of the grooves 54 are inter-connected by a bore 60. Consequently when one piston is at its inner dead lubricate the I `supplying fuel under a chamber; lubricating'means for said pump com- '75 there is always a relief of pressure in the grooves through bore 60. This construction has the further advantage in that the cylinder block is simply and inexpensively formed. A positive lubrication of each piston without undue waste of oil is obtained as in the construction of Figs. l to 5.

It is thus apparent that in the construction of fuel injection pumps which require ahigh degrec of accuracy in manufacture, an oil sealing y device has been created which is manufacturable without the risk of waste, while at the same time a positive flow of lubrication fluid is insured from the fuel supply groove to the oil seal groove without the danger of having an undue loss of oil by leakage into the pumping chamber, or without having a failure of the pump occasioned by a deficiency in lubricant by reason of the fuel dilutingy or replacing the lubricant. Extended tests have demonstrated the fact that the pressure in the oil seal groove remains at a substantially constantvalue below the oil supply pressure.

Having now described the means by which the objects of the invention are obtained, we claim:

1. In a fuel injection pump for an internalv combustion engine, said pump having a piston slidable in a cylinder and defining a pumping chamber therein,and means for supplying fuel under a first pressure to said chamber lubricating means for said pump comprising an oil supply inlet into said cylinder remote from said chamber, means for supplying oil to said inlet underv a second pressure greater than said first pressure, an oil sealing groove in saidcylinder between said inlet and said chamber, and'means for establishing communication between `said groove and said chamber within said cylinder to reduce the pressure in said groove to a pressure intermediate said first and second pressures when said piston is at its outer dead center position.

2. In a fuel injection pump as in claim 1, said means for establishing `communication compris-v ing a channel in said piston.

3. In a fuel injection pump for an internal combustion engine, said pump having a piston slidable in a cylinder and defining a pumping I ofV said cylinder remote from said chamber, means for supplying oil to said oil supply groove under a vpressure greater than said first pressure, and-an oil sealing groove in said cylinder wall between said oil supply groove and said chamber at a position where it is uncovered by said piston and communicates directly with said channel when said piston is at its outer dead center position to 'reduce the pressurein said sealing groove to a pressure intermediate said first and second pressures. y

5, In a fuel injection pump for an internal combustion en'gine, said pump having a piston the headof `which is recessed from its upper surface to a peripherally extending unloading channel, a cylinder in whichsaid piston slides anddenes a pumping chamber, and means for supplying fuel under a first pressure to lsaid chamber; lubricating means for said pump com'- prising anfannular,v oil supply groove in the wall of said cylinder remote from said chamber,

rmeans for supplying oil to said oil supply groove under a pressure greater than said first pressure, and an oil sealing groove in said cylinder wall between said oil supply vgroove and said chamber at a position where itis so near to said channel in said piston when said piston is at its l outer dead center position, that communication is indirectly established from said sealing groove, between said piston and the cylinder wa1l,to said channel to reduce the pressure in said sealing groove to a pressure intermediate said first and second pressures.

6. vA multi-cylinder fuel injection pump for an internal combustion engine, each cylinder having a piston slidable therein and defining a pumping l chamber, lubricating means for said pump comprising oil supply means `for each cylinder remote from said chamber, oil sealing means for eachcylinder between said oil supply means and chamber therein, and means for supplying fuel under a rst pressure to said chamber; lubricating means' for said pump comprising an annular oil supply groove in the wall of said cylinder remote from said chamber, means' for supplying oil to saidoil supply groove under a second pressure greater ,than saidgfirst pressure; an annular oil sealing'groove in said cylinder wall between saidv oil supply groove and said means for establishing communication between saidsealing groove and said chamber, within said to reduce the pressure in saidsealing intermediate said first and cylinder, groove to a pressure second pressures during the movement of said piston adjacent its outerdead center position.

4. In a fuel injection pump for an internal combustionl engi-ne, said pump having a 'piston the lhead of which is recessed 'from its upper surface to a peripherally extending unloading channel, a cylinder in which saidv piston slides and defines a pumping chamber, and means for rst pressure to said chamber, and j said chamber, and means for providing constant direct communication between all of said oil sealing means;

'l'. A multi-cylinder fuel injection pump for 4an internal combustion engine, each cylinder having a piston slidable therein and defining, a pumping chamber, lubricating vmeans for said pump comprising oil supply means for each `cylinder remote from said chamber, an oil sealing groove for each cylinder positioned between said supply means and said chambenand a channel common to all of said grooves and providing communication therebetween.

8.. A fuel pump comprising two elements consisting ofl a cylinder and a piston slidable therein, and defining a pumping chamber, means for supplying fuel at anrst pressure to said chamber, lubricating means for said pump comprising a lubricant supply inlet into said cylinder remote from said chamber, means to supply` a ,lubricant to said inlet at a second pressure greater piston is adjacent I- faces of the elements opposite said grooves tting to each other at.,all times from its outer dead tightly with respect when said piston is away point'. y

AUGUST LICHTE.y

`ERNST KOLBE.

prising an annular oil supply groove in the wall pressure, said elements having two 

